Medical grade dimethylsiloxane in combination with a catalyst forms an elastomer capable of delivering therapeutic levels of biologically active materials through mammalian membranes.
Transdermal drug delivery is the diffusion of a therapeutic agent into and through the skin of a mammal. It is an alternative route of administration to oral delivery of various drugs. Advantages of this type of delivery system over oral administration include lack of gastrointestinal problems, reduction of drug metabolism due to initial bypass of the liver, and the ability to continually deliver a systemic amount of a drug over a controlled period of time.
U.S. Pat. No. 3,993,073 to Zaffaroni, A., issued Nov. 23, 1976, discloses a drug delivery device for releasing drug at a controlled rate for a prolonged period of time to produce a local or systemic physiological or pharmacological effect; U.S. Pat. No. 4,460,371 to Abber, H., issued July 17, 1984, discloses a pressure sensitive adhesive; U.S. Pat. No. 4,472,372, to Keith, A. D. and Snipes, W., issued Sept. 18, 1984, discloses a polymeric diffusion matrix containing chlorpheniramine maleate, U.S. Pat. No. 4,559,054 to Bruck, S. D., issued Dec. 17, 1985, discloses a drug release device employing a block copolymer of poly (ether-urethane)/poly (dimethylsiloxane); U.S. Pat. No. 4,592,753 to Panoz, D. E., issued June 3, 1986, discloses a sustained release drug delivery device; U.S. Pat. No. 4,601,893 to Cardinal, J. R., issued July 22, 1986, discloses an improved device for the controlled and prolonged release of at least one active agent to an ambient environment; European patent No. 178212, to Caron, D. and Shroot, B., published Apr. 16, 1986, discloses various pharmaceutical carriers.
The aforementioned disclosures describe various polymeric materials, including medical grade poly (dimethylsiloxane), used as inert carriers for active substances and which in some cases are controllably released from these carriers.
Typically, medical grade poly (dimethylsiloxane) polymers are prepared by vulcanization (polymerization) of medical grade dimethylsiloxane in the presence of stannous octoate catalyst (catalyst M (Dow Corning)). This method of preparation is well-known in the art. See, for example, U.S. Pat No. 4,043,339, and references cited therein.
However, basic drugs such as, for example, chlorpheniramine and diphenhydramine cannot be incorporated into an elastomer of poly (dimethylsiloxane) because the basic drugs interact with the stannous octanoate catalyst used in the curing process and inhibit its vulcanization action.